The present invention relates to an apparatus for controlling a vehicle having a plurality of power sources and a transmission in which a gear ratio can be controlled on the basis of a driving condition such as, for example, a load against a power source of a vehicle, a vehicle speed, etc.
A power source or power sources such as, for example, an internal combustion engine or/and an electric motor, etc. are installed in a vehicle. Since characteristics of such a power source do not necessarily satisfy an output power required over the entire range of a vehicle from starting to high speed running, a transmission is mounted in the vehicle in addition to the power source in order to increase or reduce driving torque or a rotation speed of the power source. As one example of the transmission, an automatic transmission, which is automatically controlled to shift gears according to a running condition of the vehicle, is adopted in many cases. Furthermore, in accordance with a required improvement of power output characteristics or a required reduction of fuel consumption of the vehicle, the smallest gear ratio of the automatic transmission tends to be smaller than 1. A revolution of the power source can be reduced in high speed running of the vehicle, owing to the above-mentioned automatic transmission.
In the aforementioned background, there is a current tendency for an automatic transmission to have multiplied shift gears. One example of such an automatic transmission is shown in Japanese Laid-Open Patent Application No. 8-177994. The automatic transmission shown in this Patent Application, has a structure mainly having 3 sets of planetary gears, and 5th gear and 6th gear are overdrive gears. Furthermore, rotation speeds of rotating members of the automatic transmission in 6th gear are restrained low.
In the automatic transmission with six forward gears, the gear ratio of the highest gear (i.e. the smallest gear ratio of the automatic transmission) is smaller than a gear ratio of the highest gear ratio of an automatic transmission with five forward gears. Since engine revolutions in a vehicle having the automatic transmission can be reduced, the fuel consumption of the vehicle is improved during high speed driving. Furthermore, since excessive high rotation speeds of rotating members can be avoided, a durability of the automatic transmission is improved.
Since the gear ratio of 6th gear, as the highest gear, is low, however, the driving torque of the vehicle in 6th gear is low. 6th gear is set, when a load of the engine is low (i.e. a throttle angle or accelerator angle is low) and a speed of the vehicle is rather high. Consequently, even though the speed of the vehicle reduces only by a little, or the engine load increases only by a little by depressing an accelerator pedal of the vehicle, for example when the vehicle enters into a slope, a down-shift of the automatic transmission from 6th gear to 5th gear occurs, because a driving condition of the vehicle enters into a range of 5th gear. If the speed of the vehicle is higher or the engine load is lower by pulling back the accelerator pedal after the down-shift happens, the up-shift of the automatic transmission occurs, because the driving condition of the vehicle again enters into a range of 6th gear.
As mentioned above, from the viewpoint of a fuel efficiency of the vehicle it is advantageous that the automatic transmission has multiple shift gears. On the contrary, however, an up-shift or a down-shift of the automatic transmission frequently occurs, caused by only a little fluctuation of the driving condition of the vehicle. Such a phenomenon is called xe2x80x9cbusy-shiftxe2x80x9d. That is, a driver of the vehicle might feel uncomfortable, because of the busy-shift.
It is thus one object of the present invention to solve the aforementioned problems. That is, the object of the invention is to provide an apparatus for controlling a vehicle with a plurality of power sources and an automatic transmission, which prevents the automatic transmission from the above-mentioned busy-shift caused by a lower gear ratio of the highest gear. Another object is to provide a method for controlling the vehicle.
An apparatus controls a vehicle comprising at least one wheel, a first power source, a second power source, an electric power supply, and a transmission between the wheel and at least one of the power sources. The transmission transmits driving power to the wheel. The apparatus comprises a detecting means and a torque change means. The detecting means detects a selected gear ratio of the transmission. The torque change means increases or decreases a torque of the second power source in response to the selected gear ratio of the transmission.
Since torque of the second power source is increased or decreased in response to the selected gear ratio which is detected by the detecting means, a fluctuation of the driving torque of the vehicle is restrained low. Consequently, a frequent gear shift (called xe2x80x9cbusy-shiftxe2x80x9d) can be avoided.
If the detecting means detects a condition that causes power outputted by the second power source to fall and a suitable control mode for such a condition is selected, the undesirable influence caused by the fall of the power can be reduced.